Meteorological application of a dense GNSS network utilizing atmospheric delay gradient and crustal subsidence: The 2018 disastrous rain episode in SW Japan 大気遅延勾配と地殻上下変動を利用した稠密 GNSS 網の気象学的応用：平成 30 年 7 月豪雨の事例研究 by Syachrul Arief シャフルル・アリーフ A thesis submitted for the degree of Doctor of Philosophy Department of Natural History Sciences, Graduate School of Science, Hokkaido University September 2020